3D display has become a major trend in the display field. The basic principle of the stereoscopic display is to produce a stereoscopy by utilizing a parallax, i.e., to make a viewer's left eye see a left-eye image and right eye see a right-eye image, where the left-eye image and the right-eye image here are a pair of stereoscopic images with parallax. A so-called 3D display device makes the left and right eyes receive two 2D (2-dimension) images having the parallax, respectively, so that a 3D image can be perceived after the brain acquires different 2D images.
In prior art, there are two ways to manufacture a birefringent grating for the 3D display device. The first way is in that: coating an alignment layer on a glass substrate followed by rubbing; next, preparing a concave lens film on another glass substrate; then, performing a rubbing treatment on the concave lens film (as an alternative, an alignment layer may be coated, however, the currently available material for the alignment layer may dissolve the material of the concave lens film, and thus, the rubbing treatment is performed directly on the concave lens film in practice); next, assembling the two substrates and injecting liquid crystals into a space therebetween; and orienting and curing the liquid crystals. The second way is in that: preparing a layer of transparent electrode on a glass substrate; forming an alignment layer on the layer of transparent electrode and then performing a rubbing treatment; forming a layer of transparent electrode on another glass substrate followed by forming a concave lens film; then performing a rubbing treatment (as an alternative, an alignment layer may be coated, however, the currently available material for the alignment layer may dissolve the material of the concave lens film, and thus, the rubbing treatment may be performed directly on the concave lens film in practice); next, assembling the two substrates and injecting liquid crystals into a space therebetween, wherein the deflection of the liquid crystals is controlled by applying a voltage to the transparent electrodes of the two substrates so as to achieve 3D display.
In a manufacturing process for a conventional birefringent grating of the 3D display device, the rubbing and orienting of a concave lens film are factors affecting the 3D display quality. For a general TN (twisted nematic) type LCD, an angle between a polarization direction of emitting light of a polarizer and a horizontal plane is 45 degrees. And for an IPS (in-plane switching) type LCD, an angle between a polarization direction of emitting light of a polarizer and a horizontal plane is 90 degrees or zero degree. An angle between a ridge direction of the concave lens film of the birefringent grating and the horizontal plane is θ, which is generally different from the angle between the polarization direction of emitting light of the polarizer and the horizontal plane, however, in the birefringent grating of such a 3D display device, it is required that the orientation of the liquid crystal molecules is parallel to the polarization direction of emitting light of the polarizer, which means that a rubbing direction forms a certain angle with the ridge direction of the concave lens film, as shown in FIG. 1. Thus, a part of rubbing furs may rub peak positions of the concave lens film, and some of the rubbing furs may rub valley positions of the concave lens film. Generally, a width of the concave lens film is very narrow, and the valley is deep. In this case, the liquid crystal molecules at the valleys can not be well oriented and thereby the 3D display effect is substantially degraded.